© Cambridge University Press 2009. Humans rely on social interactions with others to fulfill fundamental social, psychological, and survival needs. These interactions provide basic survival needs for mating, food, and protection, but also provide the higher-order socioeconomic advantages of cooperation and reciprocity. Perhaps most importantly, however, social interactions provide individuals with a sense of belonging and recognition from their mates. Not all social interactions are pleasant, yet they still provide a sense of recognition, and in some cases belonging. For instance, aversive forms of interpersonal interaction such as bullying and overt forms of rejection still provide the individual with a sense of recognition and importance. Others must go out of their ways to bully, to overtly reject, and this expended effort alone is substantiation that one deserves recognition. However, another aversive interpersonal behavior deprives the individual of the sense of recognition and meaning: ostracism. We define ostracism as being ignored and excluded (Williams, 1997, 2001, 2007, 2009). Ostracism can occur through the physical banishment or exile of an individual or group to venues that are separate from the others. In this sense, extreme forms of segregation could be viewed as physical ostracism. Ostracism can also occur without physical separation. When society's actions communicate to individuals or groups that they are psychologically invisible and inaudible to the larger society, they become socially ostracized. By being marginalized in this way, they have no measurable impact on their society. They are not recognized, nor do they have voice.